Although you may still find references to them, including the current IB Bio materials/tests, mesosomes are generally considered artifacts of electron microscope processing and probably serve no function in living cells.

The term "envelope" includes the plasma membrane directly around the cytoplasm and the cell wall, if present.

Bacterial cell walls can be quite varied - generally made of peptidoglycan (protein and carbohydrate), they can be (a) thick and external, or (b) thin and surrounded by a lipoprotein (lipid/protein) external membrane. Different variations on this wall structure reflect adaptations to the great diversity of bacterial habitats.

Another optional outer structure is a secreted coating of slime, known as a capsule, which may help bacterial in attaching to their environment or to each other.

Projections coming off of the cell are also varied, including flagella (long and functioning for movement), pili (short, thick and functioning for connecting to other cells) and fimbria (short and thin and functioning for attachment and absorption of nutrients)

5. TOK moment - alternate ways of thinking about cells...

British artist, Luke Jerrum has created pieces using structural data for various disease causing bacteria, viruses and micro-organisms. In this interview, he discusses the balance between beauty and repulsion, as well as the importance of visual images in understanding an otherwise invisible world.

Good sources for animations of these processes (much better to see transport in action - it is not a static event, but a living process!)

1. Try this site (called "Teachers' Domain", but you are allowed!) to review all modes of transport in one animation - click on the molecules to see them move, click on components of the membrane to learn about them. 2. johnkyrk.com - especially good for structure of the membrane, but stick with it and you'll see nice views of transport across a membrane too!3. Concept mapping of major terms related to membrane transport. Take a moment to compare your brain map to others' might give you a new insight and understanding. 4. Here's a (mostly) unlabelled fluid mosaic model image with which to test yourself:

5. Animation review of types of transport across the plasma membrane

6. Nice animation of phospholipid micelles (aggregates of the PL's with hydrophillic phosphates exposed and hydrophobic fatty acids on inside) fusing to make bilayer and eventually a membrane as it would surround cell cytoplasm. (J Szostak, MGH/HHMI)

2004 Nature Publishing Group Pietzsch, J. Mind the membrane. Horizon Symposia: Living Frontier, 1-4 (2004). This is a very useful source of "Scitable" images from a highly respected publisher, Nature Publishing Group. Definitely check it out for citations for lab reports.

Stick with this video demonstration...it gives an updated version of water transport across a membrane and a very nice animation showing both animal and plant cells and how they respond to being in high (hypertonic) or low (hypotonic) solute conditions.

Prezi on Topic 2.4 - try it for review

2.5

Cell Division - Mitosis and Cancer

Quirky but informative animation...especially good in the emphasis on the cell cycle as a whole. (don't worry - starts with black screen)

Questions to consider:

1. Differentiate between cell cycle and mitosis2. How does the cell (both nucleus and cytoplasm) prepare for mitosis?3. Cancer can be thought of as mitosis gone awry - research two type of genes that cause cancer - p. 68, Biozone workbook.4. Normal cells stop dividing after 50 cell cycles or so (more on the mechanism for this later when we get to DNA/chromosome structure). Some cells stop in a more programmed way - programmed cell death. Is this a good or a bad thing - research on p. 71, Biozone book. Research other tissues that utilize PCD (also called apoptosis) on the internet.Contrast apoptosis with necrosis.

David Agus TED talks, New Strategy in the War on Cancer (2010). Questions to accompany the video.And...the 3 years later appearance on Daily Show...

or...from the bioengineer's perspective (perhaps the most impacting presentation)

And even more recently...

Cell Division Data Collection: Cancer Cell Cams!

Click on this image to go to a REAL time cell cam image of human melanoma cells growing in culture. Images are uploaded every ten minutes throughout the day. Compare this to the Bacteria Cam on the same site. Bacteria replicate so rapidly that these images are uploaded every minute!